Internally unsaturated perfluoroolefins and preparation thereof



United States Patent 'INTERNALLY UNSATURATED PERFLUOROOLE- FINS ANDPREPARATION THEREOF Warren John Brehm, Keith George Bremer, HerbertSousa Eleuterio, and Robert Walter Meschke, all of Wilmington, DeL,assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware No Drawing. Application February 27, 1958 rSerial No. 717,820

14 Claims. (Cl. 260-6533) rination, by the pyrolysis of such polymers aspolytetra'- fluoroethylene, or by the pyrolysis of low boilingperfiuoroolefins or perfiuoroalkanes such astetrafluoroethylene,hexafluoropropylene, hexafluoroethane, etc. Thesemethods, however, are economically not attractive since they involveeither the use of expensive starting materials or give rise to thedesired products in only low yields.

It is therefore one of the objects of the present invention to preparecompletely fluorinated solvents; it is another object of the presentinvention to prepare completely fluorinated olefins having highstability which are,

liquid atrooni temperature and are chemically substantially inert. It isa further object of the present invention to provide a simple andeconomic process for the preparation of completely fiuorinated solvents.Other objects will become apparent hereinafter.

The objects of the present invention are accomplished by a process whichcomprises contacting a terminally unsaturated perfluoroolefin having atleast 3 carbon atoms with catalyst-solvent combinations comprising (a)halides and hydroxides of metals of group I of the periodic table ofelements as catalysts in combination with solvents of the classconsisting of N,N-dialkylamides, N,N-dialkylphenylamines anddialkylsulfoxides and (b) quaternary ammonium salts having the generalformula R NX where R is a hydrocarbon radical and X is an anion ascatalysts in combination with inert solvents of the class consisting ofhydrocarbons, N,N-dialkylamines' and .N,N-dialkylamides at a temperatureof 0 to200 C. and recovering internally unsaturated perfiuoroolefins.The catalysts employed in the present invention are compounds which arestrongly nucleophilic. Some of the listed solvents t which are alsostrongly nucleophilic, such as dimethyl sulfoxide, may consequently beemployed in the process without a catalyst, although in general only lowyields are obtained. Although not catalytically active as a class, otherspecific nucleophilic compounds, such as methanol, may also be employed.In particular embodiments the process of the present invention comprisesreacting hexafluoropropylene with the said catalyst-solvent combinationsand recovering internally unsaturated dimers and trimers ofhexafiuoropropylene having the empirical formulas C 1 and C F g,respectively.

The metals of the metal halide and hydroxide catalysts employed in theprocess of the present invention are those found infgroup l of theperiodic table of elements (Men delett's Periodic Table, as disclosed inthe Handbook of Chemistry and Physics, Chemical Rubber PublishingCompany, 37th edition) and include, in addition to the alkali metals,gold, silver and copper. Although all halides may be employed, thepreferred halides are the fluorides and bifluorides. The quaternaryammonium compounds employed as catalysts in the process of the presentinvention are preferably halides and hydroxides.-

The solvents suitable in the process of the present invention are, asstated hereinabove, alkyl-substituted amides, phenylamines andsulfoxides with the metal halide catalysts and hydrocarbons,alkyl-substituted amides and amines with the quaternary ammoniumcompounds. The alkyl substitution has no critical effect on the reactionitself and, consequently, any alkyl substituted amide phenylamine andsulfoxide may be employed as along as it is liquid at reactionconditions. Preferably, substituted amides, amines, phenylamines andsulfoxides are employed which have alkyl substituents of one to threecarbon atoms. Similarly, the acyl radical in the substituted amide isnot critical, may be greatly varied and includes such acyl radicals asthe formyl-, acetyl-, propionyl-, butyryl-, and benzoyl radical. Allhydrocarbon solvents, liquid atreaction conditions may be employed-l Thenovel products obtained by the process .of :the present invention aredimers and trimers of perl luo ro CFa and the trimers of the presentinvention have the fore mulas Although themechanism leading to theformationof the internal double bond is not clearly understood, it isbelieved that the internally unsaturated dimers and trimers are formedby the reaction of a perfiuoroiso'propyl anion with hexafluoropropyleneor correspondingly with the dimer of hexafiuoropropylene. The resultingunstable molecule looses a fluoride ion to form the stable olefin. Thereaction mechanism appears to favor the loss of a fluoride ion from anon-terminal carbon, however, loss from a terminal carbon also appearsto be possible. This is shown by the fact that the presence of theterminally unsaturated dimers having the formulas C Fa and was detectedin the reaction mixture. It was, as a matter of fact, discovered thatthe process of the present invention could be utilized to isomerize alltypes of terminally unsaturated perfluoro'olefins andomega-hydroperfiuoroolefins into internally unsaturated pertluoroolefinsand 1- hydroperfluoroolefins respectively. Isomerization from one formof internally unsaturated dimer or trimer to another typeo'f unsaturateddimer; or trimer wasalso found to be possible employing the process ofthe. present invention.

The reaction is specific both with respect to the solvent employed andthe catalyst employed. The reaction is preferably carried out attemperatures of 25 to 100 C. for periods of 1 to 6 hours. The pressureemployed is Analysis of the dimer boiling at 50.5 C. showed a strongband in the 5.9 micron region of the infrared spectrum indicating theexistence of a double bond. Oxidation of this dimer in an aqueous mediumat 100 C.

not critical and any pressure, preferably above atmosfor two hours usingalkaline sodium permanganate repheric pressure, is suitable. Thequantity of the solvent sulted in the formation of fiuoroform andpentafluoroemployed is not critical but it is preferred to employ atethane. Thus the structure of the dimer boiling at least weight percentof solvent on the basis of the 50.5 C. was determined to beperfluoro-Z-methylpenreactant charged. The catalysts are generallyemployed tene-2 in quantities varying from 0.001% to 10% by weight 10ofthe reactants charged. However, these limits are not CF3 C=CF OFZ CFcritical to the preparation of the novel compounds of the I presentinvention.

The invention is further illustrated by the following examples" EXAMPLEI This structure was further confirmed by nuclear magnetic resonance.

Into a 320 ml. stainless steel reaction vessel was The trimer fractionwas similarly distilled and three charged under a blanket of nitrogen ata temperature of trimers were identified which boiled at l056 C., 110 C.--50' C. the solvent and quantity thereof, the catalyst and 114 C.,respectively. The trimer boiling at 110 C. and quantity thereof and theperfiuoroolefin and quanshowed a strong band at 6.05 microns in theinfrared tity thereof indicated in the table below. The reactionspectrum. Oxidation of the trimer by the method devessel was heated tothe reaction temperature indicated scribed above gave rise to theformation of 2-hydrofor a period of time also indicated with agitation.The heptafiuoropropane and fluoroform. These results are productsobtained on discharge separated into a solvent consistent with thestructure of the trimer being perand fluorocarbon layer. Thefluorocarbon layer was isofluoro-2,3,5-trimethylhexene-3. The structurewas furlated, washed with water and dried over anhydrous ther confirmedby nuclear magnetic resonance. sodium sulfate. Similar studies werecarried out on the trimer boiling Table 1 Quantity Quantity QuantityReaction 'Reaetion Rum? Perfluoro-oiefln oiporflu- Solvent of Catalystof' tempr'ratimein Weight of:

oro-olefin solvents catalyst ture in hours Productsing,

ing. inml. ing. O.

1 hexafluoropropylene 75 dimethylformamide.-. 100 26 100 6 2 100 150 1lh HJEEg. a (in 25 5 100 2 8.9. 4 one 75 1 100 2 21 (13ml) 5 -.do 75 1100 2. 98(65ml) a n 75 0.1 m0 2 90(60m1) 7 .do 75 2 1 00 2 32(20m1) a dn5 100 2 9 Co 60 5 100. 2 90. 10 do 150 dimethyl aniline 100 MeOH lml.100 2 {figgggg- 11 rln 75 dimethylformamide 75 (CH3)4NC] 1 100 2 71. 12.do 75 75 KHF, 5 28 2.5 1's fln 75 Benzene 200 dilauryldimethyl- 5 200 367.

ammoniumchloride.

75 dimethylforrnamide... 75 2 100 3 70.

75 cyclohexane 75 5 200 3 65.

75 N,N-diruethyl aniline. 75 benzyltrirnethylam- 1 100 2 72.

monium hydroxide 75 dim0thylsulf0xide' 100. 2 48.5. 75dimethylformamide". 100 v 2 38.5.

The crude, washed and dried products obtained were distilled. A dimerfraction boiling at 46 to 50 C. and a trimer fraction boiling at 105 to114 C. were obtained. The dimer fraction obtained was redistilledthrough a 100 theoretical plate Podbielniak column. There were obtainedtwo dimers having boiling points at 46 C. and 50.5 C. respectively.Infrared analysis of the dimer boiling at 46 C. showed absence of a bandat 5 to 7 microns indicated either a lack of unsaturation or an internaltrans-unsaturation. Raman analysis showed an intense band at 1730 cm.-thus indicating that there was an internal double bond. Oxidation ofthis dimer in an aqueous medium at 100 C. for two hours using alkalinesodium permanganate resulted in the formation of fiuoroform andZ-hydroheptafiuoropropane. In accordance with the teachings of La Zerteet al. (Journal of American Chemical Society 75, 4525, 1953) theoxidation results confirmed the structure of the dimer to beperfluoro-4-methylpentene-2 CFsCFCF=CF-CF' lFs Further confirmation wasobtained by nuclear magnetic resonance analysis.

at 114 C. Infrared analysis showed a strong band at 6.17 microns andoxidation with alkaline sodium permanganate resulted in the formation offluoroform. The structure of the trimer boiling at 114 C. is thusconsistent With perfiuoro-2,3,S-trimethylhexene-Z, which was furtherconfirmed by nuclear magnetic resonance.

A third trimer having a boiling point of C. to 106 C. was found to havean infrared band at 5.98 microns. The nuclear magnetic resonanceanalysis indicated the olefin to be perfluoro-2,4,5-trimethylhexene 2.

EXAMPLE II has 1...,

EXAMPLE 1n EXAMPLE IV Into a reaction vessel was charged ml. of8-hydroperfluorooctened, having a boiling point at 70 to 72 C., 100 ml.of dimethylformamide, and 1 g. of potassium bifluoride. The reactionmixture was stirred for a period of 16 hours at room temperature. Thefluorocarbon layer was separated, washed and dried and distilled througha spinning band column. There was obtained 7.5 ml. of product boiling at62 to 64 C. The compound was identified as l-hydroperfluorooctene-l.

EXAMPLE V Into a glass vessel equipped with stirrer, thermometer and gasinlet was charged 5 g. of potassium bifluoride and 75 ml. ofdimethylformamide. The system was flushed with hexafluoropropylene andagitation initiated. The hexafluoropropylene pressure was maintained at1 to 40 mm. Hg and the reaction temperature was maintained at 25 to 30C. The run was contained for 2.5 hours giving rise to 71 g. liquidproduct. On distillation, there was obtained 14.3 g. ofhexafiuoropropylene dimer comprising 98% perfluorol-methylpentene-Z and2% of perfluoro-2-methylpentene-2 and 56.7 g. of hexafluoropropylenetrimer comprising 44% of perfluoro-2,3,5-trimethylhexene-3 and 51%perfiuoro-2,3,5-trimethylhexene-Z.

The internally unsaturated perfiuoroolefins obtained by the process ofthe present invention are extremely useful as solvents in view of theirvolatility and chemical and heat stability. Thus the perfluorocarbons ofthe present invention have been heated to 650 C. without decomposition.They have been heated in the presence of air at a temperature of 350 C.for an extended period of time Without decomposition. The double bond ofthe perflucroolefins of the present invention was found to be verystable. Homopolymerization of these fluoroolefins with knownpolymerization techniques was found to be unsuccessful. Althoughcopolymerization of the perfluorocarbons of the present invention withethylene and other ethylenic compounds is feasible, extremely severereaction conditions must be employed. The compounds of the presentinvention are therefore useful as solvents and as reaction media,particularly where fiuorinated compounds are employed. The fluorocarbonsof the present invention may further be employed as refrigerants.

In addition to forming the novel dimers and trimers ofperfluoropropylene, the process of the present invention may be employedto isomerize perfiuoroolefins to internally unsaturated olefins. Thenovel compounds, thus obtained may be employed as intermediates in thepreparation of other valuable compounds through attack on the internaldouble bond.

We claim:

1. Internally unsaturated perfiuorocarbons having structures of theclass consisting of said perfluorocarbons having one ethylenic doublebond, said ethylenic bond being between non-terminal carbon atoms.

2. An internally unsaturated perfiuorocarbon having the structure saidperfluoroolefin having one ethylenic double bond, said ethylenic bondbeing between non-terminal carbon atoms.

3. Perfiuoro-4-methylpentene-2.

4. Perfiuoro-2-methylpentene-2.

5. An internally unsaturated perfiuorocarbon having the structure lll CCC said perfluoroolefin having one ethylene double bond, said ethylenicbond being between non-terminal carbon atoms.

6. Perfluoro-Z,3,5-trimethylhexene-3.

7. Perfluoro-2,3,5-trimethylhexene-2.

8. Perfiuoro-2,4,S-trimethylhexene-Z.

9. The process of preparing internally unsaturated perfiuoroolefinswhich comprises contacting a terminally unsaturated perfluoroolefinhaving at least 3 carbon atoms with a catalyst-solvent combination ofthe class consisting of (a) halides and hydroxides of metals of group Iof the periodic table of elements as the catalyst in combination withsolvents of the class consisting of N,N-dialkylamides,N,N-dialkylphenylamines and dialkylsulfoxides, and (b) quaternaryammonium compounds having the general formula NR X where R is ahydrocarbon radical and X is an anion as the catalyst component incombination with inert solvents of the class consisting of hydrocarbons,N,N-dialkylamines and N,N-dialkylamides at a temperature of 0 to 200 C.and recovering an internally unsaturated perfluoroolefin.

10. The process as set forth in claim 9 wherein the terminallyunsaturated perfiuoroolefin is hexafluoropropylene.

11. The process of preparing internally unsaturated perfluoroolefinswhich comprises contacting hexafluoropropylene with a catalystcomprising an alkali metal halide in the presence of a solvent selectedfrom the class consisting of N,Ndialkylamides and dialkylsulfoxides,said alkyl groups having from 1 to 3 carbon atoms at a temperature of Oto 200 C., and recovering a mixture of internally unsaturatedperfluoroolefins having the formulas CGFIZ and C F 12. The process asset forth in claim 11 wherein the alkali metal halide is an alkali metalfluoride.

13. The process as set forth in claim 12 wherein the alkali metalfluoride is an alkali metal bifiuoride.

14. The process of preparing internally unsaturated perfluoroolefinswhich comprises contacting hexafluoropropylene with a catalyst of theclass consisting of quaternary ammonium compounds having the generalformula R NX wherein R is a hydrocarbon radical, and X is a halogen inthe presence of an inert solvent selected from the class consisting ofhydrocarbons, N,N-dialkylamides and N,N-clialkylphenylamines, said alkylgroups having from 1 to 3 carbon atoms at a temperature of to 200 C.,and recovering a mixture of internally unsaturated perfluoroolefinshaving the formulas CgFm and C9F18.

References Cited in the file of this patent Miller: abstract ofapplication Ser. No. 47,553, published Jan. 8, 1952, 654 O.G. 632.

Chemical Abstracts, vol. 50, 5521c, April 25, 1956.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No2,912,501 December 1959 Warren John Brehm et al,

It is herebj certified that error appears in the-printed specificationof the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

dolcumls 3 end 4, Table I, under the heading "Queue city of periluoro o"g," 11 e 3, for "120" read 125 m 881118 table, under the heading"Solvent", lines 9 211' 1 4, strike out leaders and insert instead dotame, under the heading "Catalyst", lines 14. l5, strike out leaders andinsert instead m do 5 same table, under th heading "Quantity of catalystin g.,", line 2, strikeout leaders and i e t insgggad m. mudrp=uCOlllHl'll {5, line jl, 1303i "COTJElE-ifflkjfi" read continued o Signedand sealed this 31st day of May 1960 I Q [J \L)....|.. .4 Attest:

KARL Ha AXLI'LKE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

1. INTERNALLY UNSATURATED PERFLUOROCARBONS HAVING STRUCTURES OF THECLASS CONSISTING OF
 9. THE PROCESS OF PREPARING INTERNALLY UNSATURATEDPERFLUOROOLEFINS WHICH COMPRISES CONTAINING A TERMINALLY UNSATURATEDPERFLUOROOLEFIN HAVING AT LEAST 3 CARBON ATOMS WITH A CATALYST-SOLVENTCOMBINATION OF THE CLASS CONSISTING OF (A) HALIDES AND HYDROXIDES OFMETALS OF GROUPS 1 OF THE PERIODIC TABLE OF ELEMENTS AS THE CATALYST ISCOMBINATION WITH SOLVENTS OF THE CLASS CONSISTING OF N,N-DIALKYLAMIDES,N,N-DIALKYLPHENYLAMINES AND DIALKYLSULFOXIDES, AND (B) QUATERNARYAMMONIUM COMPOUNDS HAVING THE GENERAL FORMULA NR4X WHERE R IS AHYDROCARBON RADICAL AND X IS AN ANION AS THE CATALYST COMPONENT INCOMBINATION WITH INNERT SOLVENTS OF THE CLASS CONSISTING OFHYDROCARBONS, N,N-DIALKYLAMINES AND N,N-DIALKYLAMIDES AT A TEMPERATUREOF 3* TO 200*C. AND RECOVERING AN INTERNALLY UNSATURATEDPURFLUOROOLEFIN.